In general, a wrist exerciser includes a housing, a ring and a rotor. The housing includes a rail, and the ring is slidably disposed on the rail. The rotor includes a ball and a shaft. The shaft penetrates the ball, and two ends of the shaft that are opposite to each other are pivoted to the ring. The wrist exercisers utilize the principle of a gyroscope. When a spinning of the wrist exerciser is initiated by a mechanical way, the ball starts spinning in the interior of the housing and a strong spinning force generated by the centrifugal force and the inertia of the ball. Therefore, the user's wrists and shoulders are trained by resisting the spinning force.